MAP

Thursday, 23 January 2014

"Heavy metal in the early cosmos" - 9 hours ago by Aaron Dubrow

Ab initio: "From the beginning.“ It is a term that's used in science to describe
calculations that rely on established mathematical laws of nature, or
"first principles," without additional assumptions or special models.

But when it comes to the phenomena that MilosMilosavljevic is interested in
calculating, we're talking really ab
initio, as in: from the beginning of time onward.

Things were different in the early eons of the universe.
The cosmos experienced rapid inflation; electrons and protons floated free from
each other; the universe transitioned from complete darkness to light; and
enormous stars formed and
exploded to start a cascade of events leading to our present-day universe.

Working with ChalenceSafranek-Shrader and Volker Bromm at the University of
Texas at Austin, Milosavljevic recently reported
the results of several massive numerical simulations charting the forces of the
universe in its first hundreds of millions of years using some of the world's
most powerful supercomputers, including the National Science Foundation-supported
Stampede, Lonestar and Ranger systems
at the Texas Advanced Computing Center.

The results, described in the Monthly Notices of the
Royal Astronomical Society in January 2014, refine how the first galaxies formed, and in
particular, how metals in the stellar nurseries influenced the characteristics
of the stars in the first galaxies.

"The universe formed at first with just hydrogen
and helium," said Milosavljevic. "But then the
very first stars cooked metals and after those stars exploded, the metals were
dispersed into ambient space."

Eventually the ejected metals fell back into the
gravitational fields of the dark matter haloes, where they formed the second
generation of stars. However, the first generation of metals ejected from
supernovae did not mix in space uniformly.

"It's as if you have coffee and cream but you don't
stir it, and you don't wait for a long enough time," he explained.
"You would drink some cream and coffee but not coffee with cream. There
will be thin sheets of coffee and cream."

According to Milosavljevic, subtle effects like these governed the evolution of
early galaxies. Some stars formed that were rich in metals, while others were
metal-poor. Generally there was a spread in stellar chemical abundances because
of the incomplete mixing.

Another factor that influenced the evolution of galaxies
was how the heavier elements emerged from the originating blast. Instead of the
neat spherical blast wave that researchers presumed before, the ejection of
metals from a supernova was most likely a messy process, with blobs of shrapnel
shooting in every direction.

"Modeling these blobs properly is very important
for understanding where metals ultimately go," Milosavljevic said.

Predicting future observations

In astronomical terms, early in the universe translates
to very far away. Those fugitive first galaxies are unbelievably distant from
us now, if they haven't been incorporated into more recently-formed galaxies
already. But many believe the early galaxies lie at a distance that we will be
able to observe with the James Webb Space Telescope (JWST), set to launch in
2018. This makes Milosavljevic and his team's
cosmological simulations timely.

"Should the James Webb Space Telescope integrate
the image in one spot for a long time or should it mosaic its survey to look at
a larger area?" Milosavljevic said. "We want
to recommend strategies for the JWST."

Telescopes on the ground will perform follow-up studies
of the phenomena that JWST detects. But to do so, scientists need to know how
to interpret JWST's observations and develop a protocol for following up with
ground-based telescopes.

Milosavljevic and others' cosmological simulations will help
determine where the Space Telescope will look, what it will look for, and what
to do once a given signal is observed.

Distant objects, born at a given moment in cosmic
history, have tell-tale signature—spectra or light curves. Like isotopes in
carbon dating, these signatures help astronomers recognize and date phenomenon
in deep space. In the absence of any observations, simulations are the best way
of predicting these light signatures.

"We are anticipating observations until they become
available in the future," he said.

If done correctly, such simulations can mimic the
dynamics of the universe over billions of years, and emerge with results that
look something like what we see... or hope to see with new farther-reaching
telescopes.

"This is a really exciting time for the field of
cosmology," astronomer and Nobel Laureate Saul Perlmutter said in his keynote
address at the Supercomputing '13 conference in November. "We are now
ready to collect, simulate and analyze the next level of precision data...
There's more to high performance computing science than we have yet
accomplished."

Understanding our place in the universe

In addition to the practical goals of guiding the James
Webb Space Telescope, the effort to understand these very early stars in the
first galaxies has another function: to help tell the story of how our solar
system came to be.

The current state of the universe is determined by the
violent evolutions of the generations of stars that came before. Each
generation of stars (or "population," in astronomy terms) has its own
characteristics, based on the environment it was created in.

The Population III stars, the earliest that formed, are
thought to have been massive and gaseous, consisting initially of hydrogen and
helium. These stars ultimately collapsed and seeded new, smaller, stars that
clustered into the first galaxies. These in turn exploded again, creating the
conditions of Population I stars like our own, chock full of materials that
enable life. How stars and galaxies evolved from one stage to another is still
a much-debated question.

"All of this was happening when the universe was
very young, only a few hundred million years old," Milosavljevic said. "And to
make things more difficult, stars—like people—change. Every hundred million
years, every 10 million years—it's like a kid growing up, all the time
something new is happening."

Simulating the universe from birth to its current age, Milosavljevic and his team's
investigations help disentangle how galaxies changed over time, and provide a
better sense of what came before us and how we came to be.

Said Nigel Sharp, program director in the Division of
Astronomical Sciences at the National Science Foundation: "These are novel
studies using methods often ignored by other efforts, but of great importance
as they impact so much of what happens in later cosmology and galaxy
studies."

1 comment:

“Heavy metal in the early cosmos” I am fully agreed with it. Free electrons, protons, neutrons, dark energies are present in early as well as present cosmos. In early time they are more with us, now they are comparatively less. Actually they are fluctuating in a definite pattern.Presently they are more near Galactic core (just outside), near Heliosphere, near speedily rotating heavenly body."The universe formed at first with just hydrogen and helium” but development of black hole results in the fast conversion of lighter element into heavier one, specially in stars during formation.I also agree that the ejected metals fell back into the gravitational fields of the dark matter haloes, where they formed 2nd generation of stars but chances of heavy metals in it is very less.

I have worked on Dark energy & Dark matter like Where they form? How they form? How they interact with White matter? On the basis of it many mysteries of GR - Quantum will solved like- Reason of Gravitation? Why Einstein mathematically correct but logically wrong? How planets are formed in our SS? How Galaxies are formed? Role of Black hole in Galaxy. What are the different stages or types of Galaxy? How stars move from Galactic Disk to Galactic Halo? & many more.. My work is important because I am thinking out of box, I am looking the Universe from another window (of Dark Matter & Dark Energy) while our scientific window is different but on many topic we are drawing the same picture of universe.